Optical-thermal-acoustic micro-flow pump based on metamaterial absorber and preparation method of optical-thermal-acoustic micro-flow pump

Abstract

The invention relates to the technical field of microfluidics, in particular to a light-heat-sound microflow pump based on a metamaterial absorber and a preparation method of the light-heat-sound microflow pump. The technical key points are as follows: a bottom metal film, a dielectric layer and a top metal structure array are sequentially formed on a substrate to prepare the metamaterial absorber chip with the plasmon photothermal effect; spin-coating the metamaterial absorber chip with polydimethylsiloxane, and carrying out drying and curing treatment to obtain the metamaterial absorber chip with a light-taking effect; the optical-thermal-acoustic micro-flow pump with the fluid driving and mixing capabilities can be obtained by irradiating the metamaterial absorber chip with the optical effect by using laser, non-contact, remote and high-precision driving of micro-fluid is realized, and the optical-thermal-acoustic micro-flow pump has the technical effects of simple structure, high driving efficiency, high response speed and no need of complex external equipment.

Description

Technical Field

[0001] This invention relates to the field of microfluidics, specifically to a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber and its fabrication method. Background Technology

[0002] Microfluidics, a cutting-edge interdisciplinary field integrating engineering, physics, chemistry, and biology, focuses on the precise and efficient manipulation of fluids within microscale (typically micrometer-level) channels. After decades of development, this technology has demonstrated immense application potential in numerous fields, including point-of-care diagnostics, high-throughput drug screening, single-cell analysis, and environmental monitoring, thanks to its significant advantages such as low sample and reagent consumption, high analysis speed, and ease of integration and automation. As the core actuator of a microfluidic system, the performance of the micropump directly determines the efficiency and reliability of the entire system; therefore, developing novel and efficient microfluidic driving technologies remains a research hotspot in this field.

[0003] Currently, mainstream microfluidic pump driving methods mainly include pressure-driven, electric field-driven, magnetic field-driven, acoustic field-driven, and thermal field-driven methods. Among them, pressure-driven methods often require complex external equipment and are prone to fluid contamination; electric field and magnetic field-driven methods are limited by the physicochemical properties of the fluid and lack versatility; traditional acoustic field-driven methods mostly rely on piezoelectric materials, resulting in complex structures and high costs; while conventional thermal field-driven methods generally face bottlenecks such as weak driving strength and low control precision. Although non-contact optical driving technology has attracted some attention due to its potential for remote control, its low energy conversion efficiency and weak driving force continue to restrict its practical application in high-precision, high-efficiency microfluidic scenarios.

[0004] Therefore, developing a novel microfluidic driving mechanism that combines high driving efficiency, excellent controllability, simple structure, and strong universality has become a technical problem that those skilled in the art have long desired to solve but have yet to successfully overcome. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber and its fabrication method, which can effectively solve the problems commonly found in existing microfluidic pumps, such as complex structure, reliance on external equipment, weak driving force, low control precision, or poor biocompatibility.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a method for fabricating a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber, the method comprising:

[0008] A. A metamaterial absorber chip with plasmonic photothermal effect is fabricated by sequentially forming a bottom metal film, a dielectric layer, and a top metal structure array on a substrate.

[0009] B. Spin-coating polydimethylsiloxane onto the metamaterial absorber chip, followed by drying and curing, to obtain a metamaterial absorber chip with photogenerated effect;

[0010] C. Irradiate the metamaterial absorber chip with photogenerated effect obtained in step B with a laser to obtain a photo-thermal-acoustic microfluidic pump with driving and mixing fluid capabilities.

[0011] Furthermore, step A includes:

[0012] A1. Clean and dry the substrate;

[0013] A2. A bottom metal film is formed on the substrate by magnetron sputtering;

[0014] A3. A dielectric layer is formed on the underlying metal film by plasma-enhanced atomic layer deposition;

[0015] A4. A top-layer structure array is formed on the dielectric layer by electron beam lithography combined with magnetron sputtering, and then ultrasonically peeled off, cleaned and dried to obtain the metamaterial absorber chip with plasmon photothermal effect.

[0016] Furthermore, in step A, the gas pressure inside the sputtering chamber where the underlying metal film is sputtered onto the substrate by magnetron sputtering is 1×10⁻⁶. -4 - 1×10 -3 Pa.

[0017] The further sputtering chamber pressure is 1×10 -4 Pa.

[0018] Furthermore, in step A2, before depositing the underlying metal film, an adhesion layer is deposited on the substrate.

[0019] The adhesive layer is made of chromium and has a thickness of 8-20 nm.

[0020] Furthermore, in step A2, the underlying metal film is made of gold and has a thickness of 90-150 nm.

[0021] Furthermore, the thickness of the underlying metal film is 100 nm.

[0022] Furthermore, in step A3, the dielectric layer is made of Al2O3 or SiO2 and has a thickness of 5-10 nm.

[0023] Furthermore, preferably, in step A3, the thickness of the dielectric layer is 8 nm.

[0024] Furthermore, in step A4, the top-layer metal structure array is an array composed of gold cylinders;

[0025] The gold cylinders have a height of 50-100 nm, a diameter of 50-100 nm, and a spacing of 300-600 nm between adjacent gold cylinders.

[0026] Furthermore, the gold cylinder has a height of 80 nm, a diameter of 80 nm, and a spacing of 400 nm between adjacent gold cylinders.

[0027] Furthermore, in step B, the ratio of polydimethylsiloxane to curing agent is 10:1, the spin coating speed is controlled at 500-2000 rpm, and the curing temperature is 60-80℃.

[0028] Furthermore, the curing temperature is 65 ℃ and the curing time is 3 h.

[0029] Furthermore, in step B, the thickness of the polydimethylsiloxane film formed after spin coating is 100-400 nm.

[0030] Furthermore, in step C, the laser wavelength is 400-700 nm and the power is 5-50 mW.

[0031] Secondly, the present invention provides a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber, wherein the microfluidic pump is prepared according to the preparation method of a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber described in the first aspect, and the microfluidic pump comprises:

[0032] Metamaterial absorber chip, used to generate localized thermal energy under laser irradiation;

[0033] A polydimethylsiloxane membrane is applied to the surface of the metamaterial absorber chip to convert the localized thermal energy into mechanical vibrations to generate ultrasonic waves.

[0034] The metamaterial absorber chip consists of a substrate, a bottom metal film formed on the substrate, a dielectric layer formed on the bottom metal film, and a top metal structure array formed on the dielectric layer.

[0035] The technical solution provided by this invention has the following advantages compared with the known prior art:

[0036] 1. The plasmonic photothermal source used in this invention is based on an array chip structure of noble metal-dielectric material-noble metal, which is different from the previously dispersed noble metal nanoparticle colloid. It has a lower laser power requirement and generates a significant photoacoustic laser flow under a 10 mW pulsed laser, which is far lower than the laser power (more than 60 mW) used in the prior art of dispersing gold nanoparticles in water.

[0037] 2. The photo-thermal-acoustic microfluidic pump based on metamaterial absorber prepared in this invention has high photo-sonic performance. The maximum sound pressure generated under 10 mW pulsed laser reaches 0.14 MPa, which far exceeds the kPa level sound pressure generated by the same power. In microfluidic mixing test, it shows excellent performance in promoting rapid mixing of microfluidics.

[0038] 3. The photo-thermal-acoustic microfluidic pump based on metamaterial absorbers prepared in this invention has good non-contact properties due to its chip structure, while dispersed nanoparticles need to be added into the fluid, which leads to fluid contamination. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0040] Figure 1 Figure 1 shows the simulation structure unit diagram and physical diagram of the microfluidic pump in Embodiment 2 of the present invention. Figure 2(a) is the front view of the simulation structure unit of the metamaterial absorber, Figure 3(b) is the top view, Figure 4(c) is the three-dimensional diagram, and Figure 5(d) is the physical diagram.

[0041] Figure 2 Figure (a) is a schematic diagram of the microfluidic pump structure array in Embodiment 2 of the present invention, and Figure (b) is an SPs array with a side length of 500 μm.

[0042] Figure 3 Figures 2 and 3 are microscopic images of the micropump chip in Embodiment 2 of the present invention. (a) is an image of the gold array chip with plasmon photothermal effect under an optical microscope without PDMS coating. Figures (b)-(e) are SEM images from low magnification to high magnification.

[0043] Figure 4 This is a comparison diagram showing whether the microfluidic pump chip in Embodiment 2 of the present invention has or does not have plasmon array absorption;

[0044] Figure 5This is a schematic diagram illustrating the driving effect of the microfluidic pump on the fluid in Embodiment 2 of the present invention;

[0045] Figure 6 Figure 2 shows a schematic diagram of the structure of the supermaterial absorber microfluidic pump used in the fluid mixing device in Embodiment 2 of the present invention. Figure (a) is a physical picture of the micromixing device, and Figures (b) and (c) are schematic diagrams of the combination structure of the microfluidic pump and the micromixing device of the present invention.

[0046] Figure 7 This is a schematic diagram illustrating the enhanced fluid mixing effect of the metamaterial absorber microfluidic pump in Embodiment 2 of the present invention;

[0047] Figure 8 This is a quantitative diagram showing the enhanced fluid mixing effect of the metamaterial absorber microfluidic pump in Embodiment 2 of the present invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0049] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail. The terms “comprising,” “including,” “having,” “containing,” etc., as used herein are open-ended terms, meaning that they include but are not limited to. Unless the context clearly indicates otherwise, the expressions “a” and “an” as used herein include plural references. It should be noted that “first,” “second,” etc., are used merely for convenience of description and distinction and should not be construed as indicating or implying relative importance. The term “about” as used herein indicates a range of ±20% of the following numerical value. In some embodiments, the term “about” indicates a range of ±10% of the following numerical value. In some embodiments, the term “about” indicates a range of ±5% of the following numerical value. The invention is further described below with reference to embodiments.

[0050] Example: Refer to Figures 1 to 8 .

[0051] The photoacoustic effect combines light, heat, and sound. Its principle involves striking a photoacoustic composite material (composed of an absorption layer and an expansion layer) with a short-pulse laser. The absorption layer absorbs heat, causing its temperature to rise instantaneously, while the expansion layer undergoes elastic thermal expansion upon temperature change, generating ultrasonic waves. These ultrasonic waves transfer energy to the fluid, creating acoustic flow that drives the fluid. Metamaterials are artificial composite materials that achieve anomalous manipulation of physical fields such as electromagnetic waves, sound waves, and elastic waves through specially arranged, artificially designed subwavelength structural units. Materials with perfect absorption are called metamaterial absorbers, achieving near 100% absorption in specific wavelength bands. They are ideal photothermal conversion materials, and their core physical mechanism relies on surface plasmon resonance (SPs). Metamaterial absorbers with near-perfect light absorption characteristics are ideal candidate materials for constructing efficient photoacoustic driving sources due to their superior photothermal conversion capabilities.

[0052] This invention provides a microfluidic pump based on the photo-thermal-acoustic effect and its fabrication method. The core of the invention lies in integrating a metamaterial absorber with near-perfect light absorption characteristics with a polydimethylsiloxane membrane. Its working principle is as follows: when the composite structure is irradiated by a pulsed laser, the metamaterial absorber efficiently converts light energy into localized heat energy. This heat energy is then transferred to the tightly bonded polydimethylsiloxane membrane, inducing rapid and reversible thermoelastic expansion and contraction of the polymer material, thereby generating high-intensity ultrasound. This ultrasound generates a stable acoustic-fluidic effect within the microchannel, achieving non-contact, remote, and precise actuation of microscale fluids. This invention cleverly utilizes the superior photothermal conversion capability of metamaterials and the efficient electromechanical conversion capability of elastomers, successfully overcoming the inherent defects of traditional microfluidic pumps such as reliance on complex peripherals, weak driving force, or poor versatility. It achieves a microfluidic actuation effect that is simple in structure, high in driving efficiency, has good control precision, and excellent biocompatibility.

[0053] Example 1:

[0054] This embodiment provides a method for fabricating a microfluidic pump based on the photo-thermal-acoustic effect, as detailed below:

[0055] 1) Cleaning the substrate: Using a wet cleaning station, clean a 2 cm substrate. Place a 2 cm high-purity substrate in an ultrasonic cleaning station, pour in anhydrous ethanol and ultrasonically clean for 15 min, then put it in isopropanol and ultrasonically clean for 15 min, remove it and then put it in anhydrous ethanol and ultrasonically clean for 15 min. After cleaning, remove it and dry it.

[0056] 2) Depositing the underlying metal film: Using a magnetron sputtering system, place the cleaned substrate into the magnetron sputtering chamber. First, turn on the mechanical pump to purge air, and wait until the air pressure drops to 10. -1 After Pa, turn on the molecular pump to continue evacuating until the pressure drops to 1×10⁻⁶. -4- 1×10 -3 After Pa, argon gas is filled. Once the cavity is full of argon gas, an adhesion layer with a thickness of 8-20 nm is deposited. This step aims to enhance the adhesion between the underlying metal film and the silicon wafer, while also improving the overall performance of the coating. After the adhesion layer is deposited, another underlying metal film with a thickness of 90-150 nm is deposited.

[0057] 3) Dielectric layer deposition: The dielectric layer is thermally grown using plasma-enhanced atomic layer deposition (PEALD), and the steps include cleaning, deposition, and post-treatment. First, the substrate is cleaned to obtain an active surface; the deposition cycle consists of four steps: pulse adsorption, Ar gas purging, oxygen plasma oxidation, regeneration of hydroxyl groups, and purging again; finally, annealing is performed to densify the film.

[0058] 4) Electron beam lithography pattern: Clean the substrate, spin-coat electron beam resist and pre-bake. Then import the designed graphic file into the lithography equipment, and scan and write onto the resist using a focused electron beam. After exposure, use a specific developer to dissolve the exposed area, thereby obtaining the desired cylindrical pattern on the resist.

[0059] 5) Gold cylinders with top-coated metal structure array: Same as step 2), adjust the thickness of the gold cylinders to 50-100 nm.

[0060] 6) Stripping: Place the chip obtained in step 5) into a mixed solution of ethanol and isopropanol, sonicate for 30 min to remove excess photoresist, and finally rinse with deionized water and dry with nitrogen to obtain a metamaterial absorber chip with plasmon photothermal effect.

[0061] 7) Cleaning: Place the metamaterial absorber chip with plasmon photothermal effect obtained in step 5) in anhydrous ethanol for ultrasonic cleaning for 15 min, then rinse with deionized water and dry with nitrogen.

[0062] 8) Spin coating: Mix polydimethylsiloxane (PDMS) and curing agent at a ratio of 10:1 and stir until homogeneous. Fix the chip cleaned in step 7) onto the spin coating stage and spin at 500 rpm for 60 seconds. During this time, add PDMS dropwise. After the PDMS spreads out, spin coat at 2000 rpm for 30 seconds to obtain a metamaterial absorber chip with photogenerated effect.

[0063] 9) Curing: The chip spin-coated in step 8) is cured in an oven at 65 ℃ for 3 h to prepare a gold SPs array chip with photothermal and photoacoustic effects.

[0064] Example 2

[0065] This embodiment provides a method for fabricating a microfluidic pump based on the photo-thermal-acoustic effect, as detailed below:

[0066] 1) Cleaning the substrate: Using a wet cleaning station, clean a 2 cm substrate. A 2 cm high-purity silicon substrate was placed in an ultrasonic cleaning station, and anhydrous ethanol was poured in for ultrasonic cleaning for 15 minutes. Then it was placed in isopropanol for ultrasonic cleaning for 15 minutes. After that, it was taken out and placed in anhydrous ethanol for ultrasonic cleaning for 15 minutes. After cleaning, it was taken out and dried.

[0067] 2) Depositing the underlying metal film: Using a magnetron sputtering system, place the cleaned silicon substrate into the magnetron sputtering chamber. First, turn on the mechanical pump to purge air, and wait until the air pressure drops to 10... -1 After Pa, turn on the molecular pump to continue evacuating until the pressure drops to 1×10⁻⁶. -4 Then, argon gas is filled. After the cavity is filled with argon, a layer of chromium is first plated, with a thickness of 8-20 nm. This step aims to enhance the adhesion between the gold film and the silicon wafer, while also improving the overall performance of the plating. Gold itself is a very inert metal and has poor adhesion to most substrate materials (such as glass, silicon wafers, stainless steel, etc.), making it easy to peel off if plated directly. After the chromium plating is completed, another layer of gold film is plated, with a thickness of 90-150 nm.

[0068] 3) Dielectric layer deposition: The Al2O3 dielectric film is thermally grown using plasma-enhanced atomic layer deposition (PEALD). The steps include cleaning, deposition, and post-treatment. First, the substrate is cleaned to obtain an active surface. The deposition cycle consists of four steps: pulse adsorption, Ar gas purging, oxygen plasma oxidation to generate Al2O3 and regenerate hydroxyl groups, and purging again. Finally, annealing is performed to densify the film.

[0069] 4) Electron beam lithography pattern: Clean the substrate, spin-coat electron beam resist and pre-bake. Then import the designed graphic file into the lithography equipment, and scan and write onto the resist using a focused electron beam. After exposure, use a specific developer to dissolve the exposed area, thereby obtaining the desired cylindrical pattern on the resist.

[0070] 5) Gold cylinders with top-coated metal structure array: Same as step 2), adjust the thickness of the gold cylinders to 80 nm.

[0071] 6) Stripping: Place the chip obtained in step 5) into a mixed solution of ethanol and isopropanol, sonicate for 30 min to remove excess photoresist, and finally rinse with deionized water and dry with nitrogen to obtain a metamaterial absorber chip with plasmon photothermal effect.

[0072] 7) Cleaning: Place the metamaterial absorber chip with plasmon photothermal effect obtained in step 5) in anhydrous ethanol for ultrasonic cleaning for 15 min, then rinse with deionized water and dry with nitrogen.

[0073] 8) Spin coating: Mix polydimethylsiloxane (PDMS) and curing agent at a ratio of 10:1 and stir until homogeneous. Fix the chip cleaned in step 7) onto a spin coating stage and spin at 500 rpm for 60 s. During this time, add PDMS dropwise. After the PDMS spreads out, spin coat at 2000 rpm for 30 s to obtain a PDMS layer with a thickness of 200 nm, thus obtaining a metamaterial absorber chip with photogenerated effect.

[0074] 9) Curing: The chip spin-coated in step 8) is cured in an oven at 65 ℃ for 3 h to prepare a gold SPs array chip with photothermal and photoacoustic effects.

[0075] Figure 1 The three-dimensional structural diagram and physical diagram of the microfluidic pump chip of the present invention are shown. Figure (a) is a front view of the simulated structural unit of the metamaterial absorber, Figure (b) is a top view, Figure (c) is a three-dimensional diagram, and Figure (d) is a physical diagram.

[0076] Figure 2 It is Figure 1 The simulation structural unit is extended into an array diagram. The metamaterial absorber of this invention is a processed array rather than a structural unit. Figure (a) is an SPs array with a side length of 500 μm, and Figure (b) is an SPs array with a side length of 1000 μm.

[0077] Figure 3 Figure (a) shows a gold array chip with plasmon photothermal effect under an optical microscope, without the PDMS coating. The left image in Figure (a) shows a smaller array chip with a side length of 418 μm (slightly smaller than the preset value), while the right image shows a larger chip sample with a side length of 860 μm. Figures (b) to (e) are SEM images from low to high magnification. It can be seen that the chip surface is relatively flat, the gold disks are arranged regularly, the distance between each two adjacent disks is 400 nm, and the disk diameter is between 80 nm and 83 nm, with small errors consistent with the simulation design.

[0078] Figure 4 The fabricated array chip exhibits high absorption in the 400–700 nm wavelength range, all exceeding 90%, reaching 94.3% at 490 nm, and 93.6% in the commonly used 532 nm laser band. Absorption is significantly reduced in areas of the chip without the gold SPs array, indicating that the gold disk-shaped array structure can effectively enhance light absorption.

[0079] Figure 5The study demonstrates that under a 10 mW pulsed laser, the fluid exhibits a distinct motion trajectory, described as a photoacoustic laser flow. The fluid originates from the laser point and propagates outwards along the optical path, exhibiting symmetrical flow direction along the path and accompanied by local vortex phenomena. This conforms to the typical flow field characteristics of photoacoustic laser flows and is consistent with the flow field shape generated by photothermal effects, suggesting a potential composite enhancement mechanism. At a pulsed laser power of 10 mW, the maximum velocity reached 0.7 cm / s. In previous publicly available data on dispersing gold nanoparticles in water, photoacoustic laser flows only appeared with laser power exceeding 60 mW; before 60 mW, the flow field was almost static. This indicates that the gold array structure significantly enhances the driving effect on the fluid compared to dispersed gold nanoparticles.

[0080] Figure 6 A schematic diagram of a microfluidic pump-microfluidic mixing device is shown. Red and blue inks are injected from two inlets, and the inks are injected into the micromixer through a thin tube using a syringe. The syringe is controlled by a hydraulic lifting platform, and the thrust can be controlled by software, thereby controlling the flow rate. The microfluidic pump is attached to the bottom of the micromixing device, and the connection between the microfluidic pump and the flow channel of the micromixing device is irradiated with a pulsed laser. The mixing process is captured by a high-speed camera. Figure (a) is a physical image of the micromixing device. Figures (b) and (c) are schematic diagrams of the combined structure of the microfluidic pump and the micromixing device of this invention.

[0081] Figure 7 In the process, red and blue inks were first injected through two inlets. After approximately 1 minute of stable flow, a laser was added. The 0 s mark in the figure represents the time of laser addition. It can be seen that before the laser was added, the red and blue inks exhibited clear stratification. This is because the microchannels are extremely narrow, with an inner diameter of only about 500 μm and a very low Reynolds number. Mixing between the fluids is primarily through diffusion, and the diffusion efficiency is very low without external disturbance. After 0.5 s of laser addition, the boundary between the red and blue inks was almost invisible to the naked eye, and the color became very uniform after 2 s.

[0082] Figure 8To quantify the mixing effect of red and blue inks, the image processing software ImageJ was used to analyze the coefficient of variation (CV) of grayscale image mixtures. The core of this analysis is to characterize the uniformity of mixing by utilizing the statistical dispersion of image pixel grayscale values. In image analysis, CV is defined as the standard deviation of pixel grayscale values ​​within a region of interest divided by the average grayscale value within that region, typically multiplied by 100% to express it as a percentage (CV%). A low CV% indicates small differences in pixel grayscale values ​​within the region, resulting in a more uniform image and thus more even mixing. Conversely, a high CV% indicates large fluctuations in pixel grayscale values ​​within the region, making the image appear coarser or more speckled, indicating uneven mixing. As shown in the figure, the CV% of ink mixing in steady state is 38%. After only 0.5 seconds, the CV% drops to 14%, and after 2.5 seconds, it drops to around 7%, approximately one-quarter of the steady-state CV. Since the microchannels are semi-transparent, even with complete mixing, the collected grayscale values ​​are difficult to average, meaning the calculated CV% is unlikely to drop below 5%. Therefore, it can be concluded that activating the laser to incorporate the photothermal and photoacoustic effects of the SPs in the array chip significantly improves the fluid mixing efficiency. This demonstrates the potential of this array chip in microfluidic mixing. In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber, characterized in that the method... include: A. A metamaterial absorber chip with plasmonic photothermal effect is fabricated by sequentially forming a bottom metal film, a dielectric layer, and a top metal structure array on a substrate. B. Spin-coating polydimethylsiloxane onto the metamaterial absorber chip, followed by drying and curing, to obtain a metamaterial absorber chip with photogenerated effect; C. Irradiate the metamaterial absorber chip with photogenerated effect obtained in step B with a laser to obtain a photo-thermal-acoustic microfluidic pump with driving and mixing fluid capabilities.

2. The method for fabricating a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber according to claim 1, characterized in that, Step A includes: A1. Clean and dry the substrate; A2. A bottom metal film is formed on the substrate by magnetron sputtering; A3. A dielectric layer is formed on the underlying metal film by plasma-enhanced atomic layer deposition; A4. A top-layer structure array is formed on the dielectric layer by electron beam lithography combined with magnetron sputtering, and then ultrasonically peeled off, cleaned and dried to obtain the metamaterial absorber chip with plasmon photothermal effect.

3. The method for fabricating a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber according to claim 2, characterized in that, In step A2, before depositing the underlying metal film, an adhesion layer is deposited on the substrate. The adhesive layer is made of chromium or titanium and has a thickness of 8-20 nm.

4. The method for fabricating a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber according to claim 2, characterized in that, In step A2, the underlying metal film is made of gold and has a thickness of 90-150 nm.

5. The method for fabricating a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber according to claim 2, characterized in that, In step A3, the dielectric layer is made of Al2O3 or SiO2 and has a thickness of 5-10 nm.

6. The method for fabricating a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber according to claim 2, characterized in that, In step A4, the top-layer metal structure array is an array composed of gold cylinders; The gold cylinders have a height of 50-100 nm, a diameter of 50-100 nm, and a spacing of 300-600 nm between adjacent gold cylinders.

7. The method for fabricating a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber according to claim 1, characterized in that, In step B, the ratio of polydimethylsiloxane to curing agent is 10:1, the spin coating speed is controlled at 500-2000 rpm, and the curing temperature is 60-80℃.

8. The method for fabricating a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber according to claim 1, characterized in that, In step B, the thickness of the polydimethylsiloxane film formed after spin coating is 100-400 nm.

9. The method for fabricating a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber according to claim 1, characterized in that, In step C, the laser wavelength is 400-700 nm and the power is 5-50 mW.

10. A photo-thermal-acoustic microfluidic pump based on a metamaterial absorber, characterized in that, The microfluidic pump is prepared according to the method for fabricating a photo-thermal-acoustic microfluidic pump based on a metamaterial absorber as described in claim 1, wherein the microfluidic pump comprises: Metamaterial absorber chip, used to generate localized thermal energy under laser irradiation; A polydimethylsiloxane membrane is applied to the surface of the metamaterial absorber chip to convert the localized thermal energy into mechanical vibrations to generate ultrasonic waves. The metamaterial absorber chip consists of a substrate, a bottom metal film formed on the substrate, a dielectric layer formed on the bottom metal film, and a top metal structure array formed on the dielectric layer.

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